In a conventional apparatus of this type for centering of the angle milling head relative to the spindle which is supported in the spindle carriage there is provided a centering ring on one of two machine parts engaging a centering opening on the other machine part. In order that at temperature differences of both machine parts the centering ring always fits into the centering opening, a suitable clearance must exist. However, this clearance has disadvantageous effects on the machining precision of the machine.
In a different and known apparatus for centering and indexing an angle milling head with respect to the spindle carriage of a milling machine (compare German Pat. No. 2 045 604 which corresponds to U.S. Pat. No. 3,757,637), a centering ring is arranged for centering the angle milling head on the head. This centering ring works together with four ball roller elements which are arranged offset at 90.degree. in the spindle carriage. Such a ball roller element consists of a large main ball and several small balls, which are arranged in a ball sleeve. The main ball lies hereby on a ball bed of small balls, which can run around the entire surface of a hardened ball pan made of steel, which ball pan is constructed in the form of a saucer. The ball roller elements are radially fitted into the spindle carriage so that the main balls rest also in the case of a warm spindle carriage and cold angle milling head with a certain pretension on the centering ring. In this conventional apparatus, the centering ring must be hardened, which results in certain problems since the centering ring can easily warp during hardening. Furthermore the exact fitting of the ball roller elements into the spindle carriage requires a considerable amount of work input. The indexing is donw in this conventional apparatus by providing on the fastening flange of the angle milling head four shoulders which are offset at 90.degree. with respect to one another, which shoulders have indexing surfaces. Each one of the shoulders can be clamped between two stops which are arranged on the spindle carriage. One of the stops has several stop surfaces which are offset to one another, through which the angular position of the angle milling head can be changed with respect to the spindle carriage and thus the so-called camber of the milling tool can be adjusted. However, the transmission of the milling forces through only one shoulder is insufficient.
The basic purpose of the invention is to provide an apparatus for centering and indexing of machine tool parts, in particular angle milling heads on the spindle carriage of a milling machine of the abovementioned type, which is distinguished by a simple construction, high aligning exactness, temperature independency and good transmission of the milling forces. In a further development of the invention a change in the camber in the built-in condition of the angle milling head is thereby also possible and the angle milling heads and other additional aggregates of various machines are exchangeable among one another.
The basic purpose of the invention is attained according to the invention by the indexing elements being simultaneously also the centering elements and being constructed as four similarly constructed aligning units which are arranged offset to one another each at 90.degree. in peripheral direction, of which each consists of an aligning tab arranged on one milling machine part, preferably the angle milling head, and a fixing piece which is provided on the other milling machine part and has a groove.
Thus the new apparatus does not need a centering ring and the indexing elements are simultaneously also used for centering the angle milling head with respect to the spindle carriage. This makes the apparatus simpler in structure, wherein simultaneously the aligning exactness is increased totally independently from the temperature differences of both milling machine parts. Temperature differences can thus no longer have an effect since the temperature differences lead only to a relative movement of the aligning tabs with respect to the grooves in radial direction and not in peripheral direction. Since in each case four annular tabs are offset to one another at 90.degree. engage in corresponding grooves of the four fixing pieces, which grooves extend radially relative to the spindle and which are arranged also offset to one another at 90.degree., the center centering is always maintained, even when the annular tabs move in the grooves of the fixing pieces. Since the milling forces of a total of four aligning tabs are transmitted onto the fixing pieces which are secured in the spindle carriage, high milling forces also are absorbed alone through the form locking between the aligning elements. Also, a sample pretension of the fastening flange on the angle milling head with respect to the spindle carriage enables high milling forces to be satisfactorily transmitted. Moreover, the inventive apparatus has also the advantage that it permits the fully automatic attaching and indexing of the angle milling head on the spindle carriage.
In order to achieve optimum cutting conditions and surface quality and also to balance a certain resiliency of the angle milling head on the milling spindle, often a so-called camber adjustment is desired. The term "camber" means a slight incline of the milling tool axis with respect to the workpiece surface. The camber adjustment must be reversible depending on the running direction of the table. In order to make possible in the inventive apparatus also a camber adjustment, preferably each of the four fixing pieces is constructed as a slide member which is movable in a housing fastened in a recess in the spindle carriage along guideways which are slightly inclined in peripheral direction with respect to the spindle axis, wherein for the simultaneous adjustment of all four slide members at equally large paths of adjustment, an adjusting mechanism engages each slide member and the four adjusting mechanisms are coupled with one another. Of course, the guideways of all four slide members are hereby inclined in the same direction in peripheral direction with respect to the spindle axis. The inclination can thereby be kept very small and in increments for example to 1:100. If now all four slide members are moved simultaneously in axial direction at a certain distance, then from this results also a movement in peripheral direction with respect to the spindle. However, this movement in peripheral direction amounts only to one hundredth of the movement in the axial direction. Depending on whether the slide member is moved upwardly or downwardly, with this a camber adjustment in the one or the other direction can be carried out. Of course, this camber adjustment is only possible when the clamping mechanism between the angle milling head and spindle carriage is released.
Each slide member is preferably constructed cylindrically and the guideway in the housing is formed by an opening, the axis of which is slightly inclined in peripheral direction with respect to the spindle axis. Through the cylindrical construction of the slide members, edge pressures are avoided even during the highest load caused by the milling forces.
The fixing pieces must be aligned directly on the spindle carriage during the mounting. To achieve this, an aligning plate is provided preferably for aligning the fixing pieces, which aligning plate has four annular tabs which are offset 90.degree. to one another and fit into the fixing pieces, a centering opening which fits onto the free spindle end and an aligning surface which is arranged parallel with respect to the centering opening axis and parallel with respect to a diameter which extends through two diametrically opposite aligning tabs. By means of the aligning plate, the function of which will be described in greater detail later on, it is possible to aling the fixing pieces very exactly with respect to the spindle carriage and to secure same to the aligning plate. One can also use the same angle milling head with the same degree of exactness on a different machine and also other additional aggregates can be secured to most of the various machines having a high precision alignment capability.
Further advantageous developments of the invention are characterized in the remaining subclaims.